Fig. 10. Formation of the male-specific coelomic blood vessel in control and mutant gonads. (A-H) Confocal microsopy images of whole-mount anti-PECAM1 immunostaining of E12.5 XY (top row) and E12.5 XX (bottom row) gonads isolated from control mouse embryos (A,B) or Dkk1^-/- (C,D), Fog2^-/- (E,F) and Sf1-Cre/β-cat^flox/flox (G,H) mutants. The male-specific coelomic vessel (white arrowheads) normally develops in the control (A), Dkk1^-/- (C) and Sf1-Cre/β-cat^flox/flox testis (G). An ectopic vessel is visible (especially in the posterior region) in the XX Sf1-Cre/β-cat^flox/flox gonad (H). The vessel lacks the branches normally descending between the testis cords in XY gonads. No coelomic vessel could be seen in the Fog2-null samples (E,F; compare with Fig. 3D). (I-K) Light microscopy images of E12.5 gonads. A clear vesel (arrowheads) is seen on the coelomic surface of Sf1-Cre/β-cat^flox/flox XY (I) and Sf1-Cre/β-cat^flox/flox XX gonads (K and the higher magnification inset), but not on the Sf1-Cre/β-cat^+/flox ovary (J). Scale bars: 100 µm in A-H; 200 µm in I-K.